Physics Commons^™

Understanding The Spin-Glass State Through The Magnetic & Electronic Properties Of Mn-Doped Znte, A. Alcantara, S. Barrett, D. Matev, I. Miotkowski, A. K. Ramdas, T. Pekarak, J. T. Haraldsen

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

Project of Merit Winner

International Research Symposium Exhibitor and Honorable Mention

To gain insight into the spin-glass state of diluted magnetic semiconductors, we have examined the magnetic and electronic properties of Mn-doped ZnTe using density functional theory. Using a generalized gradient approximation, we investigate the electronic and magnetic properties for x=0, 0.25, and 0.50 doping levels using the magnetic moment of Mn2+ as guide for the dependence of the Hubbard onsite potential on the electronic structure as well as a geometry optimization to assure an anti-ferromagnetic (AFM) ground state which is consistent with a zero magnetic moment spin glass state. …

Magnetic Properties Of Mbe Grown La0.6sr0.4mno3 Thin Films, R. Marquez Tavera, C. Brannan, W. A. Ruiz, C. Kemgle, J. Payne, D. Brown, M. P. Warusawithana, T. M. Pekarek

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

Honorable Mention Winner

This project investigates the magnetic properties of a La1-xSrxMnO3 (x = 0.40) sample of high quality. This sample was grown one atomic layer at a time by Prof. Warusawithana using UNF’s Molecular Beam Epitaxy (MBE) machine. These magnetic properties are investigated over a range of temperatures from 5 to 400 K in fields up to 7 T. We make use of the techniques to analyze the sample to determine to a high degree of precision the critical temperature of the sample, we determined it to be 252 K. We further identified the saturated magnetization, remnant magnetization, and …

Monitoring The Night Sky For Iceact, Andre Sierra Alderete, John W. Hewitt, Warren Huelsnitz

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

The neutral subatomic neutrinos are astronomical messengers that can provide us information to investigate the most violent astrophysical sources: supernovas, gamma-ray bursts, and cataclysmic phenomena involving black holes and neutron stars. As these astrophysical neutrinos freely travel from their point of origin without being scattered by interstellar magnetic fields, we can analyze these particles by observing cosmic-ray air showers on the Earth’s atmosphere. These are produced by the energetic neutrinos by interacting with the air particles that produce a wavefront of Cherenkov radiation. To better identify these background neutrinos, IceCube, the South Pole Neutrino Observatory, constructed an imaging air Cherenkov …

Magnetic Properties Of Mbe Grown La1-Xsrxmno3 Thin Films Versus Bulk Crystal Data, Charles Bryant, James Payne, Calleigh Brannan, Rodolfo Marquez Tavera, Maitri P. Warusawithana

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

We have studied how the ferromagnetic transition and other magnetic properties vary with concentration. Data collected has been analyzed, using SigmaPlot software, to better evaluate reduced dimensionality effects on the magnetic behavior of lanthanum strontium manganite (La1-xSrxMnO3 or LSMO). Measurements using reflection high-energy electron diffraction (RHEED) were incorporated to verify that the crystals are high quality. We then measured the magnetic properties using our Superconducting Quantum Interference Device (SQUID) magnetometer. These magnetic properties have been analyzed to determine the characteristics of the superlattice. The primary goal has involved the magnetic data collection and analysis. Our analysis has investigated the major …

Gamma Rays From Massive Star Clusters G25 & G27, Abagael Barba, John W. Hewitt

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

Project of Merit Winner

Cosmic rays have baffled astronomers for over a century, as all potential origins have yet to be determined. Most of these galactic accelerated atomic nuclei are thought to be created in two possible fashions: from a supernova, or within a massive star cluster (MSC). In this study, we analyzed gamma-ray emission coincident with two MSCs named G25 and G27. Using NASA’s Fermi Large Area Telescope (LAT), we confirmed that the sources of gamma rays are spatially extended and emit up to the maximum energies observed by the LAT. So far, only the closest MSC to Earth …

Understanding The Spin-Glass State Through The Magnetic Properties Of Mn-Doped Znte, A. Alcantara, S. Barrett, D. Matev, I. Miotkowski, A. K. Ramdas, T. Pekarek, J. T. Haraldsen

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

Magnetic measurements on the spin-glass behavior in the bulk II-VI diluted magnetic semiconductor (DMS) ZnMnTe were made on two crystals of concentrations x = 0.43 and 0.55 taken from the same boule. Magnetization and density functional theory studies have shown paramagnetic behavior in both samples between 30 and 400 K. Below 30 K, there is a prominent peak at Tc = 15 and 23.6 K for concentrations x = 0.43 and 0.55, respectively. The splitting of the field cooled (FC) and zero field cooled (ZFC) data below this peak is indicative of a transition to a spin-glass state at low …

Extended Gamma Analysis Of Snr G330.2 + 1.0, Abagael Barba, John W. Hewitt

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

Analyzing gamma rays is an important aspect of modern astronomy and astrophysics, for they are the most powerful bands of energy on the electromagnetic spectrum. Comprehending gamma rays allows for deeper understanding of countless phenomena within our universe, such as cosmic rays. Cosmic rays are high energy particles thought to be formed via extremely violent explosions within our universe. These accelerated particles mirror conditions present in a supernova. A supernova is what occurs when a star at least 8 times as massive as our sun reaches the end of its lifespan and bursts. These explosions are the most powerful events …

Iceact Monitoring And Data Analysis, Andre Sierra Alderete, John W. Hewitt, Warren Huelsnitz

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

The goal of the IceACT project is to establish an array of small ACTs deployed at the South Pole for neutrino detection, CR composition studies and high energy gamma ray detection. The IceCube Neutrino Observatory at the South Pole has detected these massless subatomic particles called neutrinos. These high-energy astronomical messengers provide us information to investigate the most violent astrophysical sources: events like exploding stars, gamma-ray bursts, and cataclysmic phenomena involving black holes and neutron stars. In particular, these neutrinos have no charge, and can travel across the universe without being scattered by interstellar magnetic fields. The main background for …

Investigation Of The Obscure Spin State Of Ti-Doped Cdse, J. Dimuna, T. Boyett, I. Miotkowski, A. K. Ramdas, T. Pekarek, J. T. Haraldsen

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

Using computational and experimental techniques, we examine the nature of the 2+ oxidation of Ti-doped CdSe. Through stoichiometry and confirmed through magnetization measurements, the weakly-doped material of Cd1-xTixSe (x = 0.0043) shows the presence of a robust spin-1 magnetic state of Ti, which is indicative of a 2+ oxidation state. Given the obscure nature of the Ti2+ state, we investigate the electronic and magnetic states using density functional theory. Using a generalized gradient approximation with an onsite potential, we determine the electronic structure, magnetic moment density, and optical properties for a supercell of CdSe with an ultra-low concentration of Ti. …

Electronic And Magnetic Order As A Function Of Doping In Mixed-Valent La1-Xsrxmn03 Thin Films, James Payne, Dakota Brown, Calleigh Brannan, Tom Pekarek, Maitri Warusawithana

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

The rich phase diagram in mixed-valent manganites has been intensely studied in bulk crystals as a function of chemical doping. Here we study the effect of doping in La1-xSrxMnO3 thin films by varying the Sr/La ratio between samples. These thin films are grown using ozone assisted molecular beam epitaxy with carefully controlled stoichiometry for a range of doping from x = 0.0 to x = 0.5. Our electronic measurements reveal a crossover from a Mott insulator to a metallic ground state as x is increased. In the metallic ground state we observe a metal-to-insulator transition coincident with a ferromagnetic-to-paramagnetic ordering …

Improving Photon Number Resolution In Superconducting Nanowire Single-Photon Detectors With Integrated Impedance Tapers, Bladimiro E. Valbuena, Daniel F. Santavicca

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

Simulations are run to optimize the ability to resolve the number of photons detected from the pulse height by a Superconducting Nanowire Single-Photon Detector (SNSPD). This is set up in a manner that features an impedance-matching transmission line taper that provides a characteristic impedance which transitions from kΩ to 50 Ω, with the taper providing an effective load impedance that outputs pulses with not only larger amplitudes but also showed a distinct separation for multi-photon events. The first part of this project tries to computationally match the experimental results obtained by our collaborators at MIT. Once these results are achieved, …

Understanding The Magnetic Interactions Of The Zig-Zag Honeycomb Lattice: Application To Rucl3, Evan Wilson, Jason T. Haraldsen

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

The new field of Dirac quantum matter has produced a lot of interesting theories and materials, especially in the dynamics of magnetic materials. One such material is RuCl3, which is a S = 1/2 zigzag honeycomb lattice. Through inelastic neutron scattering, this material has demonstrated spin waves with an energy scale of 1.5-8.0 meV. According to literature, RuCl3 may be the realization of a new theoretical phase of matter called a spin liquid. This materials seems to fit the profile and has been investigated using a Kitaev model. In this study, we re-examine the data for RuCl3 using a standard …

Magnetic Properties Of Mbe Grown La1/3y1/3sr1/3mno3 Thin Films And Superlattices, W. A. Ruiz, C. Kengle, J. Payne, D. Brown, W. P. Warusawithana, T. M. Pekarek

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

We have investigated the magnetic properties of thin films related to the standard CMR system La2/3Sr1/3MnO3 where Y substituted for 50% of the La atoms. These La1/3Y1/3Sr1/3MnO3 films were grown as a random alloy where La, Y, and Sr atoms randomly occupied the A-site or as a superlattice where each unit-cell-thick layer stacked along the crystallographic (001) direction contained only one of the atoms La, Y, and Sr occupying the A-site. One of the key magnetic features of La2/3Sr1/3MnO3 is a prominent ferromagnetic transition near 350 K. We find the substitution of La with Y suppresses this ferromagnetic transition in …

Spin-Glass Ordering In The Diluted Magnetic Semiconductor Zn1-Xmnxte, S. Barrett, T. M. Pekarek

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

Magnetic measurements on the spin-glass behavior in the bulk II-VI diluted magnetic semiconductor (DMS) ZnMnTe were made on two crystals of concentrations x = 0.43 and 0.55 taken from the same boule. Magnetization and density functional theory studies have shown paramagnetic behavior in both samples between 30 and 400 K. Below 30 K, there is a prominent peak at Tc = 15 and 23.6 K for concentrations x = 0.43 and 0.55, respectively. The splitting of the field cooled (FC) and zero field cooled (ZFC) data below this peak is indicative of a transition to a spin-glass state at low …

Reduced Dimensionality Effects In Ferromagnetic Behavior In La1-Xsrxmno3, C. A. Brennan, M. P. Warusawithana, J. Payne, D. Brown, T. M. Pekarek

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

We study the magnetic properties of La1-xSrxMnO3 samples for concentrations x, 0 ≤ x ≤ 0.5. An analysis is done to accurately determine the transition temperature or critical temperature. Magnetic phase diagrams showing the various concentrations at different temperatures will be determined for our thin films. Using the phase diagrams for both bulk and thin film materials can show how reducing the dimensionality from the third dimension to approaching the second-dimension affects the phase diagram.